Thomas a



(No Model.)

T. A; EDISON. PROGESS OF MAKING CARBON FILAMENTS. No. 390,462. Patented Oct. 2, 1888.

Fig.1.

( 1 x we n fol UNTTTT) STATES PATENT Cerise.

THOMAS A. EDISON, OF LLEWELLYN PARK, NEW JERSEY.

PROCESS OF MAKiNG CARBON FI LAMENTS.

SPECIFICATION forming part of Letters Patent No. 390,462, dated Qctooer 2 1888.

Original application filed November 9, 1882,

265,891. (No model.)

To wZZ whom, it may concern: 1 Be it known that l, THOMAS A. Eorson, a citizen of the United States, residing at Llewellyn Park, in the county of Essex and State of New Jersey, have invented a certain new and useful Improvement in'Processes for Making Carbon Filaments,(0ase N0. 764, division of Case No. 510,) of which the following is a specification.

In my application for patent, Case No. 202, (Serial No. 2,180,) I describe an incandescing electric lamp having as the incaudescing conductor two or more carbon filaments connected in series, the advantage of such a lamp being the exceedingly high resistance which is obtained i by the use of two or. morefilainents. in series and the consequent saving in conductors by reason of the higher eleotro-motive force that may be employed with such a lamp. It is es' sential in such a lamp that the two or more carbon filaments should have the same resistance per unit of radiatingsurface in order that the filaments at every pointin their length will be raised to the same degree of incandescence by the flow of the current therethrough. I have found that if it is attempted to produce this uniformity of resistance per unit of radiatingsurface by flashing the filamentsthat is, by raising them to incandescence when surrounded by hydrocarbon-the resistance of the filaments is enormously decreased and the advantage of using two filaments in series is substantially lost, since the increase in resistanoe which can be obtained by theme of two flashed carbon filaments is not sufilciently greater than the resistance of one unflashed filament to warrant the change to a more expensive form of lamp.

. The object of my invention is to produce a method or process by which the two or more carbon filamentsdesigned for use in series in one lamp-globe can be made cLny flashed carbons and will have the same resistance per unit of radiating-surface.

My carbon filaments are made by carbonizing natural fibrous vegetable material, such as various woods, but preferably bamboo. In order to insure precise similarity in the two or more filaments intended for use in the same lamp, such filaments are made from a strip and connected in series with the same density,which might not be the case if the filaments were taken from ferent parts of the material. should then be carbonized together and under precisely the same conditions oiheht, strain, and pressure. This is accomplished by carbonizing them together infthe same mold.

In the accompanying drawings, forming a art hereof, Figure l is a view of alamp con taining two similar unfiashed carbon filaments connected in series, and Figs. 2 and 3 are Views of strips from each of which two filaments are made.

In Fig. 1, A is the inclosingglobe, and B the inner stem of an incandescing electric laterally diflamp, and 1 2 are the leading-in wires sealed in the glass of the stem B. Two similar un- The two or more filaments are The filaments flashed carbon filaments, C and C, are shown connected together in series at a and attached to the leading-in wires at b b. To produce such filaments a strip, Figs. 2 or 3, is cut lengthwise from the bamboo or other fibrous material employed, so that the same fibers of the bamboo shall run throughout the length of the two filaments. This strip is reduced to the proper size for the filaments, so that they will have a uniform cross-section throughout their incandescing portions, and then the strip is cut in two at the middle atthe point 0. The two filamentarydslanks are then carbonized under the same conditions by placing them together in the same mold, or the filament may be divided by breaking it in two at the center after carbonization.

I do not claim in this application the combination, with the inclosing-globe and the leadingin wires of an incandescent electric lamp, of two or more unflashcd carbonized filament-shaving the same resistance per unit of radiatingsuriaceinclosed within such globe said leading-in wires, since such a construction is covered by reducing such strip to the proper filamentary my application 'for patent,Gase-No. 510, Serial size, earbonizing such blanks together under No. 76,382, of which this case is a division. the same conditions, and dividing the blank What I claim as myinvention is transversely into two or more blanks before 5 'The process herein described of producing or after carbonization, substantially as set similar uniiashed carbon filaments for use in forth. series as the incandescing conductor of an This specification signed and witnessedthis electric lanip, consisting in forming two or 20th day of February, 1888.

more filamentary blanks for carbonization by THUS. A. EDISON, IO cutting from a natural fibrous vegetable ma- Witnesses:

teriahlengthwise of the fibers thereof, a strip WILLIAM PELZER,

of the length of two or more of such blanks, E. (J. R WLAND. 

